Your imagination is the limit. This tire turned into planter is the perfect example. http://theownerbuildernetwork.co/8zis:
love the cute picket fence, and unlike many rabbit playpens/ runs, this has a roof to protect pets from predators
diy stable ideas - Google-søgning
PLANTS THAT KEEP BUGS AWAY More
This would be a good idea for the paddocks so you can better keep their hay from getting eaten off the mud and also don't have to spend a ton of time on hay nets! Although, these should be a bit bigger.
Hay feeders we made, very easy and handy!!
A simple but great idea for feeding rabbits! However a tip to everyone - pellets are not ideal for feeding house rabbits!!! Most pellets even those bought a stores such as pet smart are for feeder rabbits! They often make your own rabbits obese and ill. Hay is a much better and cheaper solution!
Vermicomposting with Rabbit Manure: Harvest some rich vermicompost for the garden right under your rabbit cages.